Method of forming low temperature cofired composite ceramic devices for high frequency applications and compositions used therein

ABSTRACT

The invention relates to the use of and method of forming Low Temperature Cofired Ceramic (LTCC) circuits for high frequency applications. Furthermore, the invention relates to the novel LTCC thick film compositions and the structure itself.

FIELD OF THE INVENTION

The invention relates to the use of and method of forming LowTemperature Cofired Ceramic (LTCC) circuits for high frequencyapplications. Furthermore, the invention relates to the novel LTCC thickfilm compositions and the structure itself.

TECHNICAL BACKGROUND OF THE INVENTION

An interconnect circuit board is a physical realization of electroniccircuits or subsystems made from a number of extremely small circuitelements that are electrically and mechanically interconnected. It isfrequently desirable to combine these diverse type electronic componentsin an arrangement so that they can be physically isolated and mountedadjacent to one another in a single compact package and electricallyconnected to each other and/or to common connections extending from thepackage.

Complex electronic circuits generally require that the circuit beconstructed of several layers of conductors separated by insulatingdielectric layers. The conductive layers are interconnected betweenlevels by electrically conductive pathways, called vias, through adielectric layer. Such a multilayer structure allows a circuit to bemore compact.

Another useful dielectric tape composition is disclosed in U.S. Pat. No.6,147,019 to Donohue et al. The Donohue et al. dielectric tapecomposition achieves a dielectric constant in the range of 7-8 and isnot suitable as a low k material for electronic packaging signalprocessing applications.

A further useful dielectric tape composition is commercially availableProduct No. 951 (commercially available from E.I. du Pont de Nemours andCompany). Once again, this dielectric tape composition achieves adielectric constant in the range of 7-8 and is not suitable as a low kmaterial for electronic packaging signal processing applications.

Most prior art LTCC thick film materials do not achieve a sufficientlylow k to allow for use as the low k portion of an electronic package forsignal processing applications. A typical use of thick film dielectriclayers with a dielectric constant (k) of (prior art noted above detailsa k of greater than 6) is in buried passive component applications. Inthese LTCC buried passive component applications, dielectric thick filmsare common. However, in beamforming, filters, couplers, baluns, andother Radio Frequency (RF) signal processing applications which preferlower k materials than k of 7-8, so the typical materials that are usedare not LTCC materials, rather they are poly-tetra-fluoro-ethylene(PTFE) materials, such as Teflon® commercially available from E.I. duPont de Nemours and Company.

These PTFE materials can achieve a dielectric constant (k) ofapproximately 3-4. This dielectric constant of 3-4 allows for a widerline width and creates the ability to maintain 50 ohms and to achievelower dielectric loss of the circuit and lower tolerance effects fromthe screen patterning the lines. Today, low k PTFE dielectrics are usedin nearly all RF modules above 30 GHz due to wavelengths in thedielectric media being smaller.

Antennas and phased arrays are similarly designed utilizing PTFEmaterials. Antennas and phased array modules from 1 MHz up to, andincluding, mm wavelengths are used in a wide range of communication andradar applications, such as cellular telephone base stations, mobiletracking communication system, GPS, commercial broadcasting lineararrays and planar-rectangular, planar-circular radar arrays.Additionally, new cellular base station technology of smart antennas isused to improve overall communication system capacity and performance.

Military electronic intercept and related RF intelligence gatheringsystems use “beamformers” to precisely locate signal sources. They aretypically broadband to detect emissions in the range of interest.

“Beamformers” work by carefully controlling the amplitude and phase ofRF energy conveyed to the radiating elements of an antenna array.Elements commonly used to make “beamformers” are quadrature couplers,hybrid junctions, phase shifters and power dividers.

When used in conjunction with specialized receivers, “beamformer”networks can identify the location of an RF energy source.

When interfaced with suitable transducers, beamformers can be used inacoustic source location devices related to sonar. Thus, beamformers areused in many direction finding systems.

U.S. Pat. No. 5,757,611 to Gurkovich et al. discloses an electronicpackage having a buried passive component such as a capacitor therein,and a method for fabricating the same. The electronic package includes apassive component portion which includes a plurality of layers of high kdielectric material, a signal processing portion which includes aplurality of layers of low k dielectric material, and at least onebuffer layer interposed between the passive component portion and thesignal processing portion. Gurkovich et al. does not disclose an LTCCstructure which allows for the absence of a buffer layer between the lowk and high k regions. Furthermore, Gurkovich et al. discloses a methodof fabrication which utilizes pressure assisted lamination. Gurkovich etal. discloses the use of passive component portions in conjunction withsignal processing and does not disclose the ability for passivecomponent portions and signal processing as stand-alone features.Additionally, Gurkovic et al. discloses the use of capture pads alongall vertical vias between all layers.

Additionally, presently available dielectric LTCC tapes typically havean X-Y shrinkage during processing on the order of 9-13% when formedinto a multilayer circuit for high frequency applications. To minimizethe shrinkage, designers utilize constraining tapes either internally as“non-functional layers” and/or externally. Internally used constrainingtapes have a high dielectric constant in the order 15-25, which resultsin an increase in the dielectric constant of package/device overall.Externally constraining tapes require removal from the device becausethey are non-functional and the circuit surfaces are needed to add otherfunctional characteristics, such as conductors, resistors etc. Mostconstraining tapes are alumina or silica-based and they do not reactwith standard thick film dielectric tapes, if used externally. Thus,allowing for removal.

SUMMARY OF THE INVENTION

The present invention provides a low k thick film dielectric compositioncomprising, based on weight percent total inorganic composition: (1)40-80 percent glass frit with a log viscosity range of 2-6 Poise; (2)20-60 percent ceramic oxide selected from the group consistingessentially of silica, silicates, and mixtures thereof, wherein saidceramic oxide has a dielectric constant in the range of 2 to 5 k.

In one embodiment, the low k thick film dielectric composition abovefurther comprises up to 5 weight percent inorganic oxides selected fromthe group consisting of copper oxide, silicon dioxide, aluminum oxides,mixed oxides and various other such oxides. Also present may be suchproducts of mixed oxides such as aluminum silicate.

In a further embodiment, the present invention provides a method ofusing a low k thick film in the formation of a low temperature cofiredceramic structure for high frequency applications comprising the steps:

providing two or more layers of a low k thick film dielectric tape,having dielectric constant in the range of 2 to 5 and comprising, basedon solids: (a) 40-80 weight percent glass composition; (b) 20-60 weightpercent ceramic oxide; dispersed in a solution of (c) organic polymericbinder;

providing two or more layers of a high k thick film dielectric tapehaving a dielectric constant in the range of 5 to 8;

collating the layers of low k and high k thick film dielectric tapeswherein said dielectric tapes are not separated by a buffer layer;

laminating the layers of low k thick film and high k thick film to forman assembly; and

processing the assembly to form a low temperature cofired ceramicstructure.

In a further embodiment, the present invention provides the method abovewherein the glass composition consists essentially of, based on molepercent, 50-56% B₂O₃, 0.5-5.5% P₂O₅, SiO₂ and mixtures thereof, 20-50%CaO, 2-15% Ln₂O₃ where Ln is selected from the group consisting of rareearth elements and mixtures thereof, 0-6% M^(I) ₂O where M^(I) isselected from the group consisting of alkali elements; and 0-10% Al₂O₃,with the proviso that the composition is water millable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Insertion Loss comparison as a function of frequency forvarious k value materials and how a low k LTCC demonstrates loweroverall loss compared to DuPont existing LTCC materials (commerciallyavailable Product Nos. 951 and 943 from E.I. du Pont de Nemours andCompany) and compared to RO3003 (K=3), a commercially available PTFEbased system.

FIG. 2 represents a cross section view of a microwave module (Module,Board, Package) utilizing the low k thick film dielectric tape of thepresent invention.

DEFINITION OF ITEMS IN THE DRAWINGS

The numbered items in FIG. 2 are defined as follows:

-   -   (10) Surface Metalization for wirebonding, soldering, brazing,        and other post process applications as well as external RF lines        for interconnect to the Stripline section(s)    -   (20) 951 LTCC    -   (30) Interposer    -   (40) Signal Vias which connect the surface devices such is        SMT's, IC's, packaged devices and other signal processing        components to the internal microwave circuits on the internal        Low K layers which form the stripline circuits.    -   (50) Vias connecting the two stripline grounds in the LowK        region for “via fencing” for microwave designs to improve        circuit performance.    -   (60) Solid, Gridded, or partial Grounds to form the grounds for        the Stripline Sections    -   (70) Thru-All Cavities to access baseplate from surface.        Cavities from the top to place IC's or components or other        devices which would benefit from being recessed planar to the        surface of the LTCC.    -   (80) Stripline, Buried Microstrip, Covered GCPW, laminated        waveguide, and other methods for guiding propagated RF,        microwave, or mmWave Signals or using for purposes of signal        Lines for RF functions (Beamformer, Filters, antennas, couplers,        etc.    -   (90) Stripline section Low LTCC    -   (100)Baseplate for thermal dissipation and/or mechanical        strength which can be soldered, epoxied, or brazed.

DETAILED DESCRIPTION OF THE INVENTION

The present invention utilizes both high k thick film dielectric tapecompositions and low k thick film dielectric tape compositions in theformation of LTCC circuits for use in high frequency/signal processingapplications. In particular, the present invention provides novel low ktape compositions for use in the manufacture of LTCC circuits for use inhigh frequency/signal processing applications. The present inventionprovides novel compositions and methods of using and making thesecircuits.

FIG. 1 details the insertion loss comparison as a function of frequencyfor various k value materials and how a low k LTCC thick film dielectrictape of the present invention (Material 3) demonstrates lower overallloss compared to existing commercially available LTCC thick filmdielectric tape materials, Materials 1 and 2 (Product Nos. 951 and 943,commercially available from E.I. du Pont de Nemours and Company) andalso as compared to Material 4, polytetrafluoroethylene or in short PTFEmaterial, developed by E.I. duPont de Nemours Company and trade marketedas “teflon’. (Product No. RO3003, commercially available not-in-kindtechnology/PTFE with a (k=3).

In a typical case of beamformer circuits, the difference of using PTFEand LTCC-based material are listed below in Table 1. TABLE 1 Comparisonof PTFE and Novel LTCC based Technology for Beamformer CircuitApplications Typical Requirements PTFE** LTCC Balanced and stable SMT'sfor resistors either Integral Thick Film resistors planar on powerdividers/couplers on surface or in cavity internal stripline (20-30%tolerance) and for beam forming Attach packaged IC's on surface (trimmedto <5% tolerance) techniques with beamforming By processing at the timeon the same elements layer, the coupler and/or power divider Lots ofrouting and are symetrically balanced transitions between IC's and SMT'sare required Active devices on surface Packaged IC's are Bare IC's canbe attached directly to the for additional signal required, which arethen module surface and impedance matching processing (combiningsoldered to the top can be done in the LTCC next to the IC T/R withbeamformer) surface or in a cavity. wirebonds. Connectors/SMT's/Lids canbe brazed, soldered, wirebonded, and/or epoxied all on the same outerlayer on any side of module. Overall low insertion loss K = 3, LT =0.0013, very Commercial systems: K = 7.3, LT = 0.0010, betweenbeamforming stable over frequency and very stable over frequency andelements well characterized. well characterized. Post process fluids(see Process parameters like firing and above) could affect thelamination affect nominal K and LT, but dielectric and have onceunderstood, is very consistent localized areas of K Developmentalsystems: K = 3-4, LT = 0.001-0.003 change. on internal Striplinestructures Highly Mechanical Reliability; Large vias w/ donuts Vias arefilled with metal (Ag or Au (Vertical Transitions to the (more detailedimpedance based) and are sintered at 850° C. outer surface are required)matching) are required. (chemically and mechanically bonded Limitationson blind and together). NO design limitations as buried vias. comparedto PTFE vias. Vias are “mechanically” No donuts or capture pads arerequired for contacted from layer to signal vias, but capture pads arelayer, reducing the recommended on ground vias (non critical reliabilityduring thermal areas) cycle/shock. Localized areas of thermal via arrayscan Vias are hollow, and side be created for higher thermal dissipation.walls of dielectric are plated w/ Cu. = or >4 layers (= or >2 Largemetal ground Dielectric is hermetic and homogeneous. stripline regions)planes within the PTFE Conductors form a chemical and body limit theheat mecanical bond with dielectric, and are an distribution, whichcreate additive pattern (no etching/plating) on areas of local theinternal stripline layers. delamination. During the etching/platingprocess, fluids seep into the delam areas and stay there until postprocessing, such as solder reflow for SMT's and degrade reliability X-YSize <7″ square Difficult to control Flatness will be <2mils/Inchflatness/camber during lamination, when layer count is >4 layers andthere are large gnd planes for the stripline circuits**“Microwave Laminate Material Considerations for Multilayer MilitaryApplications”, R. Hornung & J. Frankosky, RF Globalnet Newsletter, 2006,Arlon Inc.

Two important components of phased array antennas are phase shifters andfeed networks. With Low K LTCC Phase shifters, performance can beimproved including power handling, losses, and bandwidth of the phaseshifters. Feed networks including series, parallel, and space can alsobe implemented. Filters using low k LTCC can now be improved upon bydesigning in lower impedance allowing wider lines, which allows foroverall better insertion loss, return loss, achieving rejection points,bandwidth In the case of Antenna Arrays path loss 88 db at 60 GHz ispushing the circuits to its limit. The only way to make up for extraloss at the higher frequencies is with the use of higher gain antennaArrays can be implemented in LTCC, but a major drawback is that mostLTCC systems have a dielectric constant>6, which lowers the gain andbandwidth of the antenna. A lower k-based LTCC (k=3 or 4) with lowerdielectric loss material has the antenna array allowing for higher gainand improved bandwidth and other improved metrics. In summary, use oflow k dielectric thick film materials either by themselves or incombination with other LTCC systems designs can be improved in the caseof Phase Shifters, Feed Networks, Frequency Scanning Arrays, WidebandArrays, Radar Phased Arrays, Beam formers, Filters, Couplers, Baluns,Power Dividers, Quadrature Couplers, Hybrid Junctions and others.Through the use of LTCC technology and the newly available low kdielectric thick film materials, layers of low k thick film dielectricmaterials may be placed in specified z locations in the electronicpackage stackup which allows for more degrees of freedom for thedesigner for RF, microwave, and mmwave signal processing.

As used herein, the terms “thick film” and “thick film paste” refer todispersions of finely divided solids in an organic medium, which are ofpaste consistency or tape castable slurry and have a rheology suitablefor screen printing and spray, dip, ink jet or roll-coating. As usedherein, the term “thick film” means a suspension of powders in screenprinting vehicles or tape castable slurry, which upon processing forms afilm with a thickness of several microns or greater. The powderstypically comprise functional phases, glass and other additives foradhesion to the substrate, etc. The vehicles typically comprise organicresins, solvents and additives for rheological reasons. The organicmedia for such pastes are ordinarily comprised of liquid binder polymerand various rheological agents dissolved in a solvent, all of which arecompletely pyrolyzable during the firing process. Such pastes can beeither resistive or conductive and, in some instances, may even bedielectric in nature. The thick film compositions of the presentinvention contain an inorganic binder as the functional solids arerequired to be sintered during firing. A more detailed discussion ofsuitable organic media materials can be found in U.S. Pat. No. 4,536,535to Usala, herein incorporated by reference. In some embodiments, fireddielectric thick film layers are on the order of 3-300 microns for asingle print or tape layer, and all ranges contained therein. In furtherembodiments, the thickness of the fired dielectric thick film layer isin the range of 3-5 microns, 5-10 microns, 10-15 microns, 30-250microns.

I. High k Dielectric Tape Composition(s)

The present invention utilizes commercially available dielectric thickfilm tape compositions as a constraining tape, either externally orinternally. These commercially available high k dielectric thick filmtapes comprise crystallizable glass-based systems such as borate-,borosilicate, or boro-phospho-silicate glass networks, as used incommercially available tape Nos. 951, 943 or tapes described in U.S.patent application Ser. No. 11/543,742, herein incorporated by reference(commercially available from E.I. du Pont de Nemours and Company). Thesecommercially available high k tapes are particularly useful in thepresent invention. As used herein, “high k” tapes are in the range of 6to 8 k. The dielectric tapes noted immediately above are not standardconstraining tapes. Standard constraining tapes, and will react with thefunctional tape layers and cannot be removed from the LTCC device,without damaging the circuits.

The high k tapes useful in the present invention are typically veryreactive and would likely react with standard constraining tapes notedabove, if used internally or externally; and therefore, high frequencyproperties such as dielectric loss and dielectric constant may degrade.Therefore, standard constraining tapes are not useful for use inconjunction with these borate-based, low loss dielectric tapes used inhigh frequency applications.

The present inventors have developed low k dielectric thick filmcompositions and methods for their use which provide (1) low dielectricloss tape for high frequency application with lower dielectric constantthan the presently available k 6-8 (2) a lower shrinkage value than thatpresently available shrinkage value of 7-12% without using aconstraining tape and (3) in some embodiments, a low k tape whichprovides the added property of constraining the high k dielectric tape(Commercially available Product Nos. 943, 951 and commercially availabletape disclosed in U.S. patent application Ser. No. 11/543,742), andfinally (4) the low k dielectric tape reacts with the high k dielectrictape and upon firing results in a continuous structure withoutdelamination and which allows the circuit designers to incorporateseveral k-value tapes at appropriate locations in the z-direction of thecircuits to control the functional property of the circuits at theappropriate locations. In some embodiments, upon firing the low k andhigh k tapes, a homogeneous structure (i.e., a structure in which theindividual tape layers are indistinguishable) results.

The present inventors have developed a novel low k and low dielectricloss tape. Furthermore the low k tape described in this invention iscompatible with the commercially available dielectric thick film tapesand could be used in specific layers of the LTCC structure. The novellow k tape has lower shrinkage than any commercially availablefunctional LTCC tapes with an additional property of constrainingpresently available other functional green tapes (for example the high kdielectric tapes disclosed above), if used in conjunction.

Typically, a LTCC tape is formed by casting a slurry of inorganicsolids, organic solids and a fugitive solvent on a removable polymericfilm. The slurry consists of glass powder(s) and ceramic oxide fillermaterials and an organic based resin-solvent system (medium) formulatedand processed to a fluid containing dispersed, suspended solids. Thetape is made by coating the surface of a removable polymeric film withthe slurry, so as to form a uniform thickness and width of coating.

In one embodiment, LTCC tape materials available for use as a dielectrictape layer in high frequency LTCC applications are disclosed in U.S.patent application Ser. No. 11/543,742, the parent application of thepresent invention to which the present invention claims priority.Furthermore, some embodiments of the dielectric thick film tapecomposition of U.S. patent application Ser. No. 11/543,742 are useful inthe present invention as the high k thick film tape layer. Thisdielectric tape is designed to eliminate potentially toxic constituentsand exhibits a uniform and relatively low dielectric constant in therange of 6-8. Additionally, the dielectric tape has a low dielectricloss performance over a broad range of frequency up to 90 GHz orsometimes higher depending on the metal loading.

II. Low k Thick Film Dielectric Tape Composition(s)

The low k tape has a very low shrinkage compared to commerciallyavailable “LTCC circuit functional tapes” and in addition, it constrainsother commercially available tapes if used in the z-direction of theLTCC structure and does not require removal after processing. The low ktape exhibits processing and materials compatibility with conductors andpassive electronic materials when used to build high density, LTCCcircuits. The low k tape system or “low k tape-based composite system”with other commercially available low loss tapes provides low dielectricloss over frequencies up to 90 GHz or higher, more circuit designfreedom than PTFE structures, superior X-Y constraining effect and goodbonding between the low k tape and high k tape without delamination oflayers under the standard processing conditions of LTCC system describedin the invention. No buffer layer is required between the thick filmdielectric tape layers of the present invention.

Overall, the present invention provides a self constrained LTCC systemwhich allows higher integration of RF, Microwave, and/or mm wave signalprocessing capability into one module, package, or board. There is noLTCC or multilayer ceramic system that exists which allows use ofmultiple high and low k dielectric layers to be used together in onecomposite module, package, or board (i.e., structure) which is selfconstrained in the X-Y direction and which also has low k and low loss.This invention will use combinations of layers consisting of varioushigh k and low k values, thicknesses, and loss values into one LTCCstructure.

Commercially available dielectric green tapes useful for LTCC deviceshave a lowest dielectric constant of approximately 6-7. Circuitdesigners are looking for a k value that is much lower than thecommercially available dielectric thick film LTCC tapes. The low Kdielectrics are used in nearly all RF modules above 30 GHz. Being ableto place layers of K lower than 6-8 in certain z locations in thestack-up allows more degrees of freedom for the circuit designer.

Antennas are now similar to those designed in PTFE due to the use oflower K dielectrics on the external layers of the module. Using lower Kallows wider RF lines to maintain a resistance of 50 ohms. This has atwo-fold impact on the designs: (1) wider lines have higher yieldsbecause the line width tolerance has a smaller effect than does anarrower line and (2) wider lines give better performance (i.e.attenuation is lower) than narrower lines.

All green tapes shrink during the LTCC processing. The shrinkage is afunction of many parameters: including particle size and particle sizedistribution of inorganic oxide present in the tape; ratio of organic toinorganic materials; kinetics of “Un-zipping” and depolymerization ofpolymers and “burn-out” of carbonaceous species; kinetics ofglass-softening; interaction of glass components to inorganic fillermaterials present in the tape, if any; nucleation and growth ofcrystals, if the glass is crystallizable. Even though shrinkage is athree dimensional phenomenon, the most important aspect for LTCC circuitdesigners is X-Y shrinkage. Preferred crystal growth has less impact onthe design. However elongated crystal growth could produce surfaceroughness, unwanted property variations. Zero X-Y shrinkage and/orcontrol of shrinkage to a lowest possible level is a desirable.Ceramicists have developed materials and tapes to control and constrainthe LTCC tapes. These constrain tapes are based on least sinterableceramic materials such as alumina and silica at the LTCC processingtemperature. Other requirements for these constraining tapes is that itshould be easily removable from the surfaces of the LTCC circuits afterthe sintering of the circuits; i.e., least reactive to the functionaltape layers. Some constraining tapes are used internally by inserting inthe Z-direction of composite layers of the functional tapes and theywill become part of the circuit and will not be removed unlike tapesused to constrain externally. All the available internally constrainingsuch tapes have high dielectric constants compared to the dielectricconstant needed for high frequency applications. The LTCC tapes used inhigh frequency applications and described in the earlier section isborate or boro-silicate, or boro-phospho-silicate glass based systemwhich will crystallize at the LTCC processing conditions, leaving behinda low viscosity “remanent glass”. The externally constraining tapesreact with the “remanent glass” so it is difficult to remove afterprocessing without damaging the circuits, and/or leaving behindresidues. Presence of such residues on the surface makes it impossibleto add functional units on the surface. So an ideal solution is todevelop a LTCC tape with a lower shrinkage value closer to zero orlowest acceptable shrinkage for design requirements without using aconstraining tape.

The applications described in 1 of this section, also need the new tapethat should be compatible with other commercially available low losstapes to mix and match several different tapes with different dielectricproperties that circuit designers' need. Furthermore the new tape shouldhave a property to constrain other high shrinkage tapes commerciallyavailable, if used in conjunction with high frequency circuits. Forexample, U.S. patent application 943 Green tape described in U.S. Pat.No. 6,147,019 and EL-0518 has a shrinkage of 9.5% when used in LTCCdevices. Without constraining, it is difficult to incorporate tapes withdifferent shrinkages into a composite for the complex electronicfunctions listed earlier.

Constraining the tape internally and/or externally and reducing theshrinkage of the composite to a minimum are the essential needs for thefuture device requirements. Standard constraining tapes cannot be usedin conjunction with these tape chemistries because they react togetherand cannot be removed after processing, thus degrading dielectricproperties: increased K, dielectric loss, and circuit surface damage ifconstraining tape is removed mechanically.

The present invention is directed to a borate, boro-silicate, or aboro-phospho-silicate crystallizable glass-based tape with ceramic oxidefiller components to control the crystallization of the glass, controlthe viscosity of the “remanent” glass, and lower the dielectric constantof the fired composite. Furthermore, the new tape may be compatible withother, commercially available low dielectric loss tapes so that they canintegrated together for several property functions.

Furthermore the new tape may be incorporated into any LTCC compositesystem with compatable chemistry if the circuit designer so desires toincorporate specific layers of lower K and low loss dielectricproperties in the circuits. Such incorporation may introducealternations in the functional property of other tape layers in thesystem.

The materials are characterized by their freedom from toxic metal oxidessuch as oxides of lead cadmium. The materials are designed to process atabout 850-875 oC useful in current tape dielectric materials. Theprocessing conditions can be adjusted for a particular LTCC circuit. Thetape is designed to cofire with conductors, buried capacitors and otherpassive electrical components applied by screen printing or tape castingor other similar processing conditions.

A. Ceramic Oxide(s)

The compositions described, that have small SiO₂ additions, have shownsignificant improvement in the compatibility with Ag based conductorlines. The tendency to interact in proximity to Ag conductor lines issuppressed in the tape compositions tested that were made from glassesthat give high viscosity “remanent glass”. The dielectric lossproperties reported unexpectedly shows that the addition of small amountof SiO₂ in the composition do not alter significantly the dielectriccharacteristics of the tape dielectric. The low addition levels of SiO₂addition to glass shown in this case was not reported in Donohue et al.U.S. Pat. No. 6,147,019. The addition of SiO₂ was indicated as notbeneficial to dielectric loss.

In the present invention, significantly higher amount of silica is addedas second crystalline phase filler to borate or boro-silicate orboro-phospho-silicate glasses to reduce the dielectric constant andgreen tape shrinkage to satisfy the low k needs of LTCC designers.

Therefore, the present invention provides a low k thick film dielectrictape composition comprising, based on wt % total inorganic composition:(1) 40-80%, preferably 45-55% borate-based or, boro-silicate, orboro-phospho-silicate-based glass composition such as glass chemistrydescribed in U.S. Pat. No. 6,147,019; EL-0518; DUPONT glass used inGreen Tape 951, or similar crystallizable glasses with a log viscosityrange at the peak firing temperature 2-6 Poise (2) 20-60%, preferably30-50% ceramic oxide or mixed oxide fillers such as silica, silicatescompatible to glass chemistry (3) 0-5% other inorganic oxides andcompounds such as copper oxide and others with similar chemistries.

B. Glass Frit

In the formulation of tape compositions, the amount of glass relative tothe amount of ceramic material is important. A filler range of 20-60% byweight is considered desirable in that the sufficient densification isachieved. If the filler concentration exceeds 60% by wt., the firedstructure is not sufficiently densified and is too porous. Within thedesirable glass to filler ratio, it will be apparent that, duringfiring, the filler phase will become saturated with liquid glass. Theglass-filler ratio variation is also depends on the viscosity of theglass at the softening point, viscosity of the “remanent glass”, and thenature of the filler to the so-called glass “net-work formers”

For the purpose of obtaining higher densification of the compositionupon firing, it is important that the inorganic solids have smallparticle sizes. In particular, substantially all of the particles shouldnot exceed 15 um and preferably not exceed 10 um. Subject to thesemaximum size limitations, it is preferred that at least 50% of theparticles, both glass and ceramic filler, be greater than 1 um and lessthan 6 um.

One embodiment of the glass composition used in this invention is aboro-phospho-silicate glass network consisting essentially of, based onmole percent, 50-56% B₂O₃, 0.5-5.5% P₂O₅, SiO₂ and mixtures thereof,20-50% CaO, 2-15% Ln₂O₃ where Ln is selected from the group consistingof rare earth elements and mixtures thereof, 0-6% M^(I) ₂O where M^(I)is selected from the group consisting of alkali elements; and 0-10%Al₂O₃, with the proviso that the composition is water millable. Anotherglass used in this invention has been described in Donahue and others inHang et al. The inorganic filler used in this invention is silica powderhas the surface area of 0.5-15.0 m2/gm preferably 7.0-13.0 m2/gm. Othermixed ceramic oxides and/or mixtures of ceramic oxides compatible to thewetting characteristics of the crystallizable glasses that have a logviscosity range 2-6 Poise at the maximum firing temperature of 850 oC.

C. Organic Medium

The organic medium in which the glass and ceramic inorganic solids aredispersed is comprised of an organic polymeric binder which is dissolvedin a volatile organic solvent and, optionally, other dissolved materialssuch as plasticizers, release agents, dispersing agents, strippingagents, antifoaming agents, stabilizing agents and wetting agents.

To obtain better binding efficiency, it is preferred to use at least 5%wt. polymer binder for 90% wt. solids (which includes glass and ceramicfiller), based on total composition. However, it is more preferred touse no more than 30% wt. polymer binder and other low volatilitymodifiers such as plasticizer and a minimum of 70% inorganic solids.Within these limits, it is desirable to use the least possible amount ofbinder and other low volatility organic modifiers, in order to reducethe amount of organics which must be removed by pyrolysis, and to obtainbetter particle packing which facilitates full densification uponfiring.

In the past, various polymeric materials have been employed as thebinder for green tapes, e.g., poly(vinyl butyral), poly(vinyl acetate),poly(vinyl alcohol), cellulosic polymers such as methyl cellulose, ethylcellulose, hydroxyethyl cellulose, methylhydroxyethyl cellulose, atacticpolypropylene, polyethylene, silicon polymers such as poly(methylsiloxane), poly(methylphenyl siloxane), polystyrene, butadiene/styrenecopolymer, polystyrene, poly(vinyl pyrollidone), polyamides, highmolecular weight polyethers, copolymers of ethylene oxide and propyleneoxide, polyacrylamides, and various acrylic polymers such as sodiumpolyacrylate, poly(lower alkyl acrylates), poly(lower alkylmethacrylates) and various copolymers and multipolymers of lower alkylacrylates and methacrylates. Copolymers of ethyl methacrylate and methylacrylate and terpolymers of ethyl acrylate, methyl methacrylate andmethacrylic acid have been previously used as binders for slip castingmaterials.

U.S. Pat. No. 4,536,535 to Usala, issued Aug. 20, 1985, has disclosed anorganic binder which is a mixture of compatible multipolymers of 0-100%wt. C₁₋₈ alkyl methacrylate, 100-0% wt. C₁₋₈ alkyl acrylate and 0-5% wt.ethylenically unsaturated carboxylic acid of amine. Because the abovepolymers can be used in minimum quantity with a maximum quantity ofdielectric solids, they are preferably selected to produce thedielectric compositions of this invention. For this reason, thedisclosure of the above-referred Usala application is incorporated byreference herein.

Frequently, the polymeric binder will also contain a small amount,relative to the binder polymer, of a plasticizer that serves to lowerthe glass transition temperature (Tg) of the binder polymer. The choiceof plasticizers, of course, is determined primarily by the polymer thatneeds to be modified. Among the plasticizers which have been used invarious binder systems are diethyl phthalate, dibutyl phthalate, dioctylphthalate, butyl benzyl phthalate, alkyl phosphates, polyalkyleneglycols, glycerol, poly(ethylene oxides), hydroxyethylated alkyl phenol,dialkyldithiophosphonate and poly(isobutylene). Of these, butyl benzylphthalate is most frequently used in acrylic polymer systems because itcan be used effectively in relatively small concentrations.

The solvent component of the casting solution is chosen so as to obtaincomplete dissolution of the polymer and sufficiently high volatility toenable the solvent to be evaporated from the dispersion by theapplication of relatively low levels of heat at atmospheric pressure. Inaddition, the solvent must boil well below the boiling point or thedecomposition temperature of any other additives contained in theorganic medium. Thus, solvents having atmospheric boiling points below150° C. are used most frequently. Such solvents include acetone, xylene,methanol, ethanol, isopropanol, methyl ethyl ketone, ethyl acetate,1,1,1-trichloroethane, tetrachloroethylene, amyl acetate, 2,2,4-triethylpentanediol-1,3-monoisobutyrate, toluene, methylene chloride andfluorocarbons. Individual solvents mentioned above may not completelydissolve the binder polymers. Yet, when blended with other solvent(s),they function satisfactorily. This is well within the skill of those inthe art. A particularly preferred solvent is ethyl acetate since itavoids the use of environmentally hazardous chlorocarbons.

In addition to the solvent and polymer, a plasticizer is used to preventtape cracking and provide wider latitude of as-coated tape handlingability such as blanking, printing, and lamination. A preferredplasticizer is BENZOFLEX® 400 manufactured by Rohm and Haas Co., whichis a polypropylene glycol dibenzoate.

Application

A green tape is formed by casting a thin layer of a slurry dispersion ofthe glass, ceramic filler, polymeric binder and solvent(s) as describedabove onto a flexible substrate, heating the cast layer to remove thevolatile solvent. This forms a solvent-free tape layer. The tape is thenblanked into sheets or collected in a roll form. The green tape istypically used as a dielectric or insulating material for multilayerelectronic circuits. A sheet of green tape is blanked with registrationholes in each corner to a size somewhat larger than the actualdimensions of the circuit. To connect various layers of the multilayercircuit, via holes are formed in the green tape. This is typically doneby mechanical punching. However, a sharply focused laser or othermethod(s) can be used to volatilize and form via holes in the greentape. Typical via hole sizes range from 0.004″ to 0.25″. Theinterconnections between layers are formed by filling the via holes witha thick film conductive ink. This ink is usually applied by standardscreen printing techniques. Each layer of circuitry is completed byscreen printing conductor tracks. Also, resistor inks or high dielectricconstant inks can be printed on selected layer(s) to form resistive orcapacitive circuit elements. Furthermore, specially formulated highdielectric constant green tapes similar to those used in the multilayercapacitor industry can be incorporated as part of the multilayercircuitry.

After each layer of the circuit is completed, the individual layers arecollated and laminated. A confined uniaxial or isostatic pressing die isused to insure precise alignment between layers. The laminate assembliesare trimmed with a hot stage cutter. Firing is typically carried out ina standard thick film conveyor belt furnace or in a box furnace with aprogrammed heating cycle. This method will, also, allow top and/orbottom conductors to be co-fired as part of the constrained sinteredstructure without the need for using a conventional release tape as thetop and bottom layer, and the removal, and cleaning of the release tapeafter firing.

The dielectric properties of the fired tape (or film) of the presentinvention depend on the quantity and/or quality of total crystals andglasses present and other factors. The low temperature co-fired ceramic(LTCC) device dielectric properties also depend on the conductor used.The interaction of conductor with the dielectric tape may, in someembodiments, alter the chemistry of the dielectric portion of thedevice. By adjusting the heating profile and/or changing the qualityand/or quantity of the filler in the tape and/or chemistry of theconductor, one skilled in the art could accomplish varying dielectricconstant and/or dielectric loss values.

As used herein, the term “firing” means heating the assembly in anoxidizing atmosphere such as air to a temperature, and for a timesufficient to volatilize (burn-out) all of the organic material in thelayers of the assemblage to sinter any glass, metal or dielectricmaterial in the layers and thus density the entire assembly.

It will be recognized by those skilled in the art that in each of thelaminating steps the layers must be accurate in registration so that thevias are properly connected to the appropriate conductive path of theadjacent functional layer.

The term “functional layer” refers to the printed green tape, which hasconductive, resistive or capacitive functionality. Thus, as indicatedabove, a typical green tape layer may have printed thereon one or moreresistor circuits and/or capacitors as well as conductive circuits.

It should also be recognized that in multilayer laminates having greaterthan 10 layers typically require that the firing cycle may exceed 20hours to provide adequate time for organic thermal decomposition.

The use of the composition(s) of the present invention may be used inthe formation of electronic articles including multilayer circuits, ingeneral, and to form microwave and other high frequency circuitcomponents including but not limited to: high frequency sensors,multi-mode radar modules, telecommunications components and modules, andantennas. The system described in the present invention allows higherintegration of microwave functions into one module, package, or board.Other Major Significance is that no other LTCC or multilayer ceramicsystem that exists which allows use of multiple dielectric layers to beused together in one composite module, package, or board. This inventionwill use combinations of layers consisting of various K values,thicknesses, loss values into one composite structure.

Multilayer Circuit Formation

The present invention further provides a method of forming a multilayercircuit comprising the steps:

wherein, said circuit achieves a x,y-shrinkage in the range of 0-5% andwherein said low k constraining tape layer has a k value in the range of2-5, and wherein said tapes allow more degrees of freedom forhigh-frequency LTCC circuit designers to mix and match several tapeswith the tapes described in this invention for specific circuitrequirements

FIG. 2 details one embodiment of the present invention-based circuit ofa microwave module. The following items are detailed in FIG. 2:

-   -   10 Surface Metalization for wirebonding, soldering, brazing, and        other post process applications as well as external RF lines for        interconnect to the Stripline section(s)    -   20 High k thick film tape    -   30 Interposer    -   40 Signal Vias which connect the surface devices such is SMT's,        IC's, packaged devices and other signal processing components to        the internal microwave circuits on the internal Low K layers        which form the stripline circuits.    -   50 Vias connecting the two stripline grounds in the LowK region        for “via fencing” for microwave designs to improve circuit        performance.    -   60. Solid, Gridded, or partial Grounds to form the grounds for        the Stripline Sections    -   70 Thru-All Cavities to access baseplate from surface. Cavities        from the top to place IC's or components or other devices which        would benefit from being recessed planar to the surface of the        LTCC.    -   80 Stripline, Buried Microstrip, Covered GCPW, laminated        waveguide, and other methods for guiding propagated RF,        microwave, or mmWave Signals or using for purposes of signal        Lines for RF functions (Beamformer, Filters, antennas, couplers,        etc.    -   90 Stripline Section of low k LTCC    -   100 Baseplate for thermal dissipation and/or mechanical strength        which can be soldered, epoxied, or brazed.

These multilayer circuits require that the circuit be constructed ofseveral layers of conductors separated by insulating dielectric layers.The insulating dielectric layer may be made up of one or more layers ofthe tape of the present invention. The conductive layers areinterconnected between levels by electrically conductive pathwaysthrough a dielectric layer. Upon firing, the multilayer structure,made-up of dielectric and conductive layers, a composite is formed whichallows for a functioning circuit (i.e. an electrically functionalcomposite structure is formed). The composite as defined herein is astructural material composed of distinct parts resulting from the firingof the multilayer structure which results in an electrically functioningcircuit.

Another circuit design by mix and match with other commerciallyavailable tapes and tape of this invention is shown below

EXAMPLES

Tape compositions used in the examples were prepared by ball milling thefine inorganic powders and binders in a volatile solvent or mixturesthereof. To optimize the lamination, the ability to pattern circuits,the tape burnout properties and the fired microstructure development,the following volume % formulation of slip was found to provideadvantages. The formulation of typical slip compositions is also shownin weight percentage, as a practical reference. The inorganic phase isassumed to have a specific density of 3.5 g/cc for glass and 2.2 g/ccfor silica and the organic vehicle is assumed to have a specific densityof 1.1 g/cc. The weight % composition changes accordingly when usingother glasses and oxides other than silica as the specific density maybe different than those assumed in this example. TABLE 2 SlipComposition wt % Inorganic Phase 73.8 Organic Phase 26.2

The above weight % slip composition may vary dependent on the desirablequantity of the organic solvent and/or solvent blend to obtain aneffective slip milling and coating performance. More specifically, thecomposition for the slip must include sufficient solvent to lower theviscosity to less than 10,000 centipoise; typical viscosity ranges are1,000 to 4,000 centipoise. An example of a slip composition is providedin Table 2. Depending on the chosen slip viscosity, higher viscosityslip prolongs the dispersion stability for a longer period of time(normally several weeks). A stable dispersion of tape constituents isusually preserved in the as-coated tape.

If needed, a preferred inorganic pigment at weight % of 0.1 to 1.0 maybe added to the above slip composition before the milling process. TABLE3 The inorganic chemical composition of the tape formulation. Tape # 1 23 Glass Powder 57% 50% 45% Silica 43% 50% 45%Glass powder used in this composition is a phospho-boro-silicate glassdescribed in commonly assigned patent application Ser. No. 11/543,742.Silica in the composition #1 and #2 has a PSD ˜1.5 (D50) and silica incomposition #3 is finer with surface area ˜8-12 m2/gm.Property Measurements: Dielectric Properties

The measurement of dielectric constant, E_(r) and dielectric loss(tangent delta) has been performed for selected samples of tape madefrom the tapes indicated in Table 2. These measurements were performedusing a (non-metallized) split cavity method in a range of frequencyfrom 3.3 GHz to 16 GHz. A reference to the measurement method is givenin “Full-Wave Analysis of a Split-Cylinder Resonator for NondestructivePermittivity Measurements” by Michael Janezic published in IEEETransactions on Microwave Theory and Techniques, Vol 47, No. 10, October1999. Data for two frequencies are provided in Table 2. The data, (E_(r)and loss), for all measured samples shows a very slight increase withfrequency. TABLE 4 Dielectric Properties of LTCC Based on InorganicMaterials Described in Table 1 along with properties of some standardLTCC tapes. Frequency of Tape ID# measurement K Loss Tangent 1 10.73 GHz3.01 0.004 2 10.44 GHz 3.94 0.003 3 LTCC (EL#518) 7.34 0.001 943-A5 (lowloss LTCC) 7.66 0.001 851-AT (standard LTCC) 7.53 0.004The dielectric constant reduced to approximately 50% however anddielectric loss is increased slightly for the LTCC tape in the currentinvention.

The dielectric properties of the fired film of this invention, which isa “devitrified glass-ceramic-glass composite”, depend on the quantityand/or quality of total crystals and glasses present in the composite.The LTCC dielectric properties also depend on the conductor film whichis a “metal-devitrified glass-ceramic composite”.

It was stated earlier, one of major contributions of this inventionshould give freedom for circuit designers to incorporate differentlayers of LTCC tapes for different function in a composite format.

Tape Shrinkage and Refire Stability

The shrinkage values have been measured then calculated using the“Hypotenuse” method, known to those skilled in the art. All parts werefired at 850° C. following a standard green tape firing profile. Severalcomposite test format have been made to demonstrate the shrinkage of thetape of this invention and its ability to constrain other commerciallyavailable tapes if incorporated within the composite.

Details of a some typical eight layer composite structures are givenbelow. A refers to 951 and B refers to 943 are commercial tapes ofDUPONT COMPANY, Wilmington, Del. E refers to the tape described inEL#518 and C refers to tape of this invention. Table 4 is arepresentation of some typical test pattern builds and Table 5 is theshrinkage of 8 layer composites after firing in a typical green beltfurnace profile. All results show up to approximately 80% moreconstraining than the shrinkage of some of the commercially availableLTCC tape. The shrinkage of the LTCC tape of this invention has ashrinkage of ˜1%. TABLE 5 Some Typical 8 layer Composite LTCC Structuresbased on Different Constraining Format:* Test Build #1 #2 #3 #4 #5 #6Tape Layer #1 A A C A A B Tape Layer #2 C C E E C C Tape Layer #3 B E EC C C Tape Layer #4 B E E E C C Tape Layer #5 B E E E C C Tape Layer #6B E E C C C Tape Layer #7 C C E E C C Tape Layer #8 A A C A A B#1, #2 & #4 are internally constraining Composite Format and #3 isexternally constraining composite format.#5 & #6 are typical circuit systems using the tape of this invention incomposite format.“C” is the Tape of this invention.“A”, “B” and “E” are commercially available tape or tapes described inU.S. Pat. App. No. 11/543742 Microstructures taken using ScanningElectron microscope of the fired film of all the composites show (1) nodelamination between the layers (2) good microstructures in terms ofgrain and grain boundaries and (3) no significant increase in the levelof porosity

TABLE 6 X-Y Shrinkage the LTCC Tape of This Inventionn (TTI) Some OtherLTCC Composites Incorporating with TTI. Eight Layer X-Y Shrinkage TapeSpecification Composite Structure (%) −951 + TTI 951 (6) + TTI (2)**4.32 −943 + TTI(#2) 943 (6) + TTI (2)** 2.42 −993 + TTI(#3) 943 (6) +TTI (2)** 0.98 −944 (1) + TTI(#2) 944 (6) + TTI (2)** 3.15 −944 (2) +TTI(#2) 944 (6) + TTI (2)** 3.20 −951 Alone 12.75 −943 Alone 9.84 −944(1)* Alone 10.92 −944 (2)* Alone 9.50*944 (1) and 944 (2) are based on two different tape chemistriesconvered in U S Patent application 11/543742 (Attorney Docket #EL-0518USNA). Finer silica-based based tape of this invention (#3) gavelower shrinkage when used in the composite structure described herecompare to tape contains coarser silica (#1 & #2)**Two layers of “tape of this invention” (TTI) are inserted anywhere ina symmertical manner as ahown in the table within the 8 layers ofcommecially available green tapes, 951, 943, & 944. TTI layers are“circuit functional layers” of the overall circuit and need not to beremoved. TTI layers could be connected with other tape layers throughvia-fill conductors, and circuit conductor lines in the conventionalmanner.Microstructure of the Fired CompositesThe microstructral analysis on Scanning Electron Micrographs of severalcombinations of low K tape and other LTCC tapes composites has shown (1)complete interfacial microstructral compatibility (2) good densificationof the low k tapes and (3) no significant microstructural defects of anykind.

Dielectric constant of two different tape formulations in a buriedcomposite form is measured. Results show the effect of conductor binderson the K values. TABLE 7 A TTI Buried Composite With DifferentConductors and Other LTCC Tape 943 Tape Conductor Low K Tape of Thisinvention Conductor 943 943 943 943 Low K Tape of This invention 943Tape

K values of the low K tape as measured within the buried form for threedifferent conductors are given below. Used vias to measure the capvalues. Results show the conductor binder effect on the dielectricconstant K values are calculated from the measured capacitor value atfrequency 1 KHz and calculated thickness values using tape shrinkagedata from table 6. TABLE 8 Variation of K values as Measured in BuriedForm With Different Conductors for the Composite format in Table 7 TapeID Glass/Filler (%) Conductor Capacitance (pF) K Tape 1 57/43 Gold 1172.7 Tape 1 57/43 Silver - 1 125 2.8 Tape 1 57/43 Silver - 2 154 3.4 Tape2 50/50 Gold 152 2.7 Tape 2 50/50 Silver - 1 236 4.2 Tape 2 50/50Silver - 1 256 4.6

1. A low k thick film dielectric composition comprising, based on weightpercent total inorganic composition: (1) 40-80 percent glass frit with alog viscosity range of 2-6 Poise; (2) 20-60 percent ceramic oxideselected from the group consisting essentially of silica, silicates, andmixtures thereof, wherein said ceramic oxide has a dielectric constantin the range of 2 to 5 k.
 2. The low k thick film dielectric compositionof claim 1 further comprising: up to 5 weight percent inorganic oxidesselected from the group consisting of copper oxide, silicon dioxide,aluminum oxides and mixed oxides.
 3. A method of using a low k thickfilm in the formation of a low temperature cofired ceramic structure forhigh frequency applications comprising the steps: providing two or morelayers of a low k thick film dielectric tape, having dielectric constantin the range of 2 to 5 and comprising, based on solids: (a) 40-80 weightpercent glass composition; (b) 20-60 weight percent ceramic oxide;dispersed in a solution of (c) organic polymeric binder; providing twoor more layers of a high k thick film dielectric tape having adielectric constant in the range of 5 to 8; collating the layers of lowk and high k thick film dielectric tapes wherein said dielectric tapesare not separated by a buffer layer; laminating the layers of low kthick film and high k thick film to form an assembly; and processing theassembly to form a low temperature cofired ceramic structure.
 4. Themethod of claim 3 wherein said glass composition consists essentiallyof, based on mole percent, 50-6% B₂O₃, 0/5-5.5% P₂O₅, SiO₂ and mixturesthereof, 20-50% CaO, 2-15% Ln₂O₃ where Ln is selected from the groupconsisting of rare earth elements and mixtures thereof; 0-6% M^(I) ₂Owhere M^(I) is selected from the group consisting of alkali elements;and 0-10% Al₂O₃, with the proviso that the composition is watermillable.
 5. A thick film tape comprising the composition of claim
 1. 6.A LTCC device comprising one or more tapes of claim 5, wherein the oneor more tapes form a signal processing section.
 7. The LTCC device ofclaim 6, wherein the tape provides X-Y constraining.
 8. The LTCC deviceof claim 6, wherein the device further comprises a constraining tape. 9.A method of using a low k thick film tape in the formation of a lowtemperature cofired ceramic structure for high frequency applicationscomprising the steps: (a) providing two or more layers of a low k thickfilm dielectric tape, wherein the tape comprises the composition ofclaim 1 dispersed in a solution of organic polymeric binder; (b)applying a conductor track on the two or more layers, and applying viasconnecting the two or more layers, forming a functional layer; (c)collating multiple functional layers; (d) laminating the collatedfunctional layers; and (e) Processing the assembly to form a lowtemperature cofired ceramic structure.
 10. The method of claim 9,wherein the LTCC device further comprises one or more high k thickfilms.
 11. The method of claim 9 wherein, after the lamination of step(d), the two or more layers of a low k thick film dielectric tape form asingle signal processing section.
 12. An LTCC device made by the methodof claim
 9. 13. A beamformer, filter, antenna, or coupler comprising theLTCC device of claim 12
 14. The beamformer of claim 13, wherein thebeamformer is used in an application selected from the group consistingof: high frequency sensors, multi-mode radar modules, telecommunicationscomponents, telecommunications modules, and antennas.
 15. Anelectrically functioning circuit comprising one or more functionallayers, wherein a functional layer comprises: (a) two or more layers ofa low k thick film dielectric tape of claim 5; and (b) a conductor trackportion, wherein the conductor track portion is on the two or morelayers of low k thick film dielectric tape, wherein vias connect the twoor more layers.
 16. The electrically functioning circuit of claim 15,wherein the circuit is a microwave module, package, or board.
 17. Theelectrically functioning circuit of claim 15, wherein the circuitfurther comprises a surface metallization.
 18. The electricallyfunctioning circuit of claim 26, wherein the two or more tape layersform a signal processing section.
 19. The electrically functioningcircuit of claim 15, wherein the tape provides X-Y constraining.
 20. Theelectrically functioning circuit of claim 15, wherein the circuitfurther comprises a constraining tape.